There is fishless cycling and there is cycling with fish. I think both take around the same time. Cycling with fish might take longer b/c people will do water changes just to keep the fish alive which delays the cycle. A cycle is finished when you have added an ammonia source, hopefully your ammonia goes to 4 ppm
, and later there is 0 ammonia and 0 nitrite. Nitrates are still toxic, but not as much as ammonia and nitrite. Most fish and definitely inverts are sensitive to high levels of nitrate too so like I said, it's best to add them when you have a reading that is fairly close to zero.